[x86] Move the vperm2f128 test to be vperm2x128 and test both the
floating point and integer domains.

Merge the AVX2 test into it and add an extra RUN line. Generate clean
FileCheck statements with my script. Remove the now merged AVX2 tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218903 91177308-0d34-0410-b5e6-96231b3b80d8